Solvated ruthenium precursors for direct liquid injection of ruthenium and ruthenium oxide

ABSTRACT

A method is provided for forming a film of ruthenium or ruthenium oxide to the surface of a substrate by employing the techniques of chemical vapor deposition to decompose ruthenium precursor formulations. The ruthenium precursor formulations of the present invention include a ruthenium precursor compound and a solvent capable of solubilizing the ruthenium precursor compound. A method is further provided for making a vaporized ruthenium precursor for use in the chemical vapor deposition of ruthenium and ruthenium-containing materials onto substrates, wherein a ruthenium precursor formulation having a ruthenium-containing precursor compound and a solvent capable of solubilizing the ruthenium-containing precursor compound is vaporized.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of application Ser. No.09/506,962, filed Feb. 18, 2000, pending, which is acontinuation-in-part (CIP) of application Serial No. 09/141,236, filedAug. 27, 1998, now U.S. Pat. No. 6,063,705, application Ser. No.09/140,878, filed Aug. 27, 1998, now U.S. Pat. No. 6,074,945, andapplication Ser. No. 09/140,932, filed Aug. 27, 1998, now U.S. Pat.6,133,159.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to chemical vapor deposition offilms of ruthenium. More particularly, the invention relates to directliquid injection of precursor solutions of ruthenium compounds for usein chemical vapor deposition of ruthenium and ruthenium oxide. Theinvention further relates to solvated ruthenium precursor formulationssuitable for forming vaporized ruthenium precursor deposition ofruthenium films onto substrates.

[0004] 2. State of the Art

[0005] Use of chemical vapor deposition (“CVD”) methods for depositing athin film of material on a substrate, such as a silicon wafer or otherexposed material surface on a wafer or other semiconductor base, arewidely known and used in the semiconductor fabrication industry. Intypical CVD processes, a precursor, such as a heat decomposable volatilecompound, is contacted with a substrate which has been heated to atemperature above the decomposition temperature of the precursor. Inthis fashion, a coating, which typically comprises a metal, metalmixture or alloy, ceramic, metal compound, or a mixture thereof,depending on the choice of precursors and reaction conditions, is formedon the substrate.

[0006] Use of CVD as a thin film formation method includes numerousdesirable characteristics, such as the ability to readily control thecomposition of the thin film and the ability to form a thin film withoutcontamination of, or damage to, the substrate. CVD may also be used todeposit films of metals into vias, trenches, and other recesses orstepped structures. In situations where conformal thin-film depositionis required, CVD techniques are a preferred method of deposition, sinceevaporation and sputtering techniques cannot be used to form a conformalthin-film deposition layer.

[0007] While CVD techniques have been described in the literature withreference to many metals and metalloids, commercial use of CVD has beenpredominantly confined to deposition of a few metals and metalcompounds, such as tungsten, silicon, titanium nitride, silicon oxide,iron, and aluminum. CVD of other metals has been limited due to avariety of reasons, including formation of poor film quality,requirement of high processing temperatures, lack of suitable precursorcompounds, and instability of the precursors used in the depositionsystems. The availability of suitable volatile and heat-decomposableprecursor compounds appears to be a significant limiting factor in theapplication of CVD to the production of metal-containing films.

[0008] In integrated circuit processing, selected precursor compoundshave been used to form conducting films that can maintain theirintegrity at elevated temperatures. Ruthenium and ruthenium dioxide(RuO₂) are particularly well-suited as conducting films for suchapplications since they have good electrical conductivities, exhibithigh stability over a wide temperature range and exhibit good adherenceto silicon, silicon dioxide, and ceramic oxides. Films of ruthenium andruthenium oxide deposited by CVD have been proposed to be useful forcontact metallizations, diffusion barriers, and gate metallizations. M.L. Green et al., J. Electrochem. Soc., 132, 2677 (1985).

[0009] There are a wide variety of ruthenium compounds that can be usedas precursors for the preparation of such films. Many are particularlywell suited for use in chemical vapor deposition techniques. Forexample, U.S. Pat. No. 5,372,849 to McCormick et al. discloses the useof ruthenium compounds containing carbonyl ligands and other ligands.However, such compounds are typically less volatile and not as easilyused in chemical vapor deposition techniques.

[0010] Another use of ruthenium precursors for the preparation of filmsinvolves use of a chemical spray deposition process whereintris(acetylacetonate)ruthenium in butanol is converted into an aerosolspray using a hydrogen/nitrogen mixture as the carrier gas. Trirutheniumdodecacarbonyl, ruthenocene, and tris(acetylacetonate)ruthenium havealso been compared as CVD precursors in the formation of ruthenium andRuO₂ by M. Green et al., in J. Electrochem. Soc., 132, 2677 (1985).However, because none of the aforementioned precursors are veryvolatile, high deposition rates using these precursors are difficult toobtain.

[0011] U.S. Pat. No. 4,250,210, issued Feb. 10, 1981 to Crosby et al.,discloses the use of ruthenium 1, 3 dione compounds, such astris(acetylacetonate)ruthenium and its fluorinated derivatives, in theCVD of ruthenium films. Although the fluorinated ligands are said toprovide greater volatility and good deposition rates when heated to over200° C., difficulties in attaining uniform coatings are noted due to thepoor stability of the precursors. Furthermore, organic byproducts withvery low vapor pressures are formed and collect in the reactor duringthe volatilization process, which can create a serious contaminationproblem in production-scale applications of thetris(acetylacetonate)ruthenium precursors.

[0012] Also disclosed in the Crosby patent is the use of rutheniumcarbonyl chloride and penta(trifluorophosphine)ruthenium as precursorsfor ruthenium CVD. Use of these precursor compounds, however, isundesirable because the obtainable rates of deposition of ruthenium arevery low and ruthenium carbonyl chloride corrodes certain substrates,making a consistent product preparation difficult or impossible.

[0013] In view of the described shortcomings, it would be useful toutilize ruthenium precursor formulas having both high stability and highvolatility that are easy to prepare and use in low temperature CVDprocesses and which are capable of depositing high-quality, continuousfilms of ruthenium having good surface morphology. While many rutheniumprecursor compounds possessing such characteristics are known, thosesame compounds typically have freezing points around room temperature.Thus, in order to prevent these ruthenium precursor compounds fromfreezing, the system typically needs to be heated. Using a solution ofruthenium precursor compounds in an organic solvent instead of the neatprecursor for a liquid delivery system would eliminate the necessity ofheating the direct liquid injection (DLI) system. These same precursorcompounds, however, are usually very temperature sensitive, with heatingat slightly elevated temperatures resulting in the decomposition of theprecursor. Side products of this decomposition are solids, which aredetrimental to a liquid delivery process as well. Also measuring andcontrolling extremely small amounts (e.g., microliter/min) of rutheniumprecursors is very difficult.

[0014] Thus, in view of the shortcomings of the available precursors, acontinuing need exists for improved ruthenium precursor formulationsuseful for the CVD of films of ruthenium and ruthenium-containing films(e.g., RuO₂, SrRuO₃, RuSi_(x)). More specifically, a need exists forhigh-volatility ruthenium precursor formulations that are highly stable,maintain a ruthenium precursor in a soluble state, and do not requireheating of the precursor formulation prior to introducing the same intoa CVD system. The precursor formulations should also be easy to prepare,easy to measure, convenient to use in low-temperature CVD processes, andavailable in more manageable delivery forms (i.e., ml/min rate).

BRIEF SUMMARY OF THE INVENTION

[0015] The present invention provides a method for applying a film ofruthenium or ruthenium oxide to the surface of a substrate by employingthe techniques of chemical vapor deposition (CVD) to decompose stableruthenium precursor formulations which include a Ru precursor compounddissolved in a solvent capable of solubilizing the Ru precursorcompound.

[0016] The method of the present invention provides an improved CVDtechnique wherein continuous Ru films of high quality and good surfacemorphology can be deposited at low temperatures by utilizing theaforementioned Ru formulations as precursors in the CVD process. In theabsence of an oxygen source, the deposited films consist essentially ofRu in that they contain only minor amounts of residual elements, thusforming essentially pure films of Ru. The aforementioned precursorformulations may be used as neat liquids, in mixtures, or in additionalsolvents for delivery by liquid injection\flash evaporation techniques.

[0017] The present invention also provides a CVD method where theprecursor formulations either contain significant amounts of oxygen orare used in combination with reactive carrier gases (e.g., oxidizerssuch as O₂ or N₂O) to deposit films of RuO₂. Ruthenium metal depositedon a polysilicon electrode can also be subjected to post-depositionrapid thermal oxidation (RTO) to cause silicidation of the bottom layerand oxidation of the top layer of the Ru film. This layer configurationcan also be formed by depositing Ru metal first (to be later silicided)and then forming an oxide thereon either in situ, through the additionof an oxidizer, or by post deposition anneal.

[0018] Alternating layers of essentially pure Ru and of RuO₂ can also bedeposited on a single substrate by selecting and alternating theprecursors or reactive carrier gases present in the environment duringthe CVD process(es).

[0019] The method of the present invention further provides a techniquefor making a vaporized ruthenium precursor for use in CVD of rutheniumand ruthenium-containing films onto substrates wherein a rutheniumprecursor formulation, having a ruthenium-containing precursor compoundand a solvent capable of solubilizing the ruthenium-containing precursorcompound, is vaporized.

BRIEF DESCRIPTION OF THE DRAWING

[0020]FIG. 1 is a schematic of a chemical vapor deposition systemsuitable for use in the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Ruthenium Precursor Formulations

[0021] In the present invention, ruthenium precursor formulationsinclude a ruthenium-containing precursor compound and a solvent capableof solubilizing the ruthenium-containing precursor compound.Illustrative examples of precursor compounds which can be used in the Ruprecursor formulation of the instant invention includecyclopentadienetricarbonyl ruthenium, cyclohexadienetricarbonylruthenium, cycloheptadienetricarbonyl ruthenium, norbornadienetricarbonyl ruthenium, cyclohexadienetetracarbonyl ruthenium,diethylenetricarbonyl ruthenium, dipropylene tricarbonyl ruthenium, andallyltetracarbonyl ruthenium. Illustrative examples of solvents whichcan be used in the ruthenium precursor formulation of the instantinvention include hexane, hexanes (e.g., a mixture of hexane isotopes),pentane, heptane, butylacetate, and derivatives and combinationsthereof. It is understood that solvents suitable for use in the presentinvention include any organic or inorganic solvent which solubilizesruthenium-containing precursor compounds without decomposing the same.

[0022] It has been found that the ruthenium precursor formulations andsolutions of the present invention prevent the ruthenium precursorcompounds from freezing at room temperature, thus, eliminating the needto heat delivery lines of the CVD apparatus and the resultingdecomposition of the ruthenium precursor compounds during the heatingprocess. Additionally, solvating the ruthenium precursor compoundsincreases the precision of the delivery system by increasing thedelivery from an inconvenient measurement rate for the neat compound,such as a microliter/min rate, to a more advantageous measuring rate,such as a ml/min rate used with the ruthenium precursor formulations ofthe present invention.

[0023] A. The CVD Process

[0024] The invention broadly relates to use of CVD to deposithigh-quality films of Ru at low temperatures on the surface of asubstrate and, more particularly, to DLI of precursor solutions into avaporizer for use in a CVD process. Methods of the present invention areparticularly well suited for CVD processes employing vapor depositiontechniques, such as flash vaporization.

[0025] The invention can be carried out through any number of known CVDprocesses requiring vaporization of precursors. Following vaporizationof the precursor formulations, CVD processes may be modified by alteringsuch variables as, for example, the heating method, gas pressure, and/orchemical reaction. Conventional CVD methods suitable for use with thesolvated Ru precursors of the present invention include both cold-walltype CVD, wherein only a deposition substrate is heated through anynumber of methods such as induction heating or use of hot stages.Alternatively, hot-wall type CVD, in which an entire reaction chamber isheated, can be used. The CVD processes can also vary with respect topressure requirements and may include atmospheric CVD, in which thereaction occurs at a pressure of about one atmosphere, or low-pressureCVD, in which reaction occurs at pressures between about 10⁻¹ to about100 torr.

[0026] It is understood that the CVD process can be carried out in anytype of apparatus in which the substrate and/or the Ru precursor isheated. CVD apparatus designs suitable for use in the precursorformulations of the present invention include, but are not limited to,hot wall reactors, cold wall reactors, plasma-assisted reactors,radiation beam assisted reactors, and the like. One such suitable CVDapparatus design, in the form of a horizontal tube CVD reactor, isschematically depicted in FIG. 1.

[0027] As shown in FIG. 1, a typical CVD process begins with theplacement of substrate 6, on which deposition is to occur, withinreaction chamber 4 of reactor 2. One or more units of substrate 6 can beheld in place within reaction chamber 4 in, for example, a verticalposition by a suitable holder 20. Substrate 6 is then heated to atemperature sufficient to decompose and vaporize the precursor complex.A vacuum (not shown), which can be created by any suitable vacuum pump,can be provided at opposite end 12 of reaction chamber 4 to create avacuum within reaction chamber 4. Precursor vapor 8 is introduced intoreservoir 10 located at one end of reactor 2 and exposed to a vacuum byopening valve 14 located between reaction chamber 4 and reservoir 10.

[0028] It should be understood that the ruthenium precursor formulationsmay be vaporized in reservoir 10 or introduced into reservoir 10 as apre-vaporized precursor. Regardless of where vaporization takes place, apreferred method for vaporization of the Ru precursors for CVD is DLI ofthe solvated Ru precursor formulations into a flash vaporizer. It hasbeen found that DLI of Ru precursor solutions of the instant inventionallows increased deposition rates for thermally unstable compounds andfacilitates the monitoring of material consumption.

[0029] Following vaporization, precursor vapor 8 then passes intoreaction chamber 4 containing one or more units of substrate 6. Reactionchamber 4 is maintained at a preselected temperature, by means of afurnace 16, which is effective to decompose precursor vapor 8 so as todeposit a film 18 containing Ru on the exposed surfaces of substrate 6.

[0030] Generally, a thermal reactor CVD system can be used to heat thesubstrate to a temperature in excess of the decomposition temperature ofthe selected Ru precursor. Thermal CVD may be effected within any typeof apparatus in which the substrate and/or the precursor is heated. Byheating the substrate at a sufficiently high temperature, thedecomposition reaction occurs at the surface of this substrate.Likewise, in an energy-beam induced CVD technique, an energy source(i.e., ion beam) is advantageously used to heat the substrate such thatthe decomposition of the precursor occurs predominantly at the substratesurface.

[0031] Use of these thermal CVD processes can provide blanket depositionof Ru on substrates. Additionally, selected area depositions of Ru maybe accomplished by using a masking material (e.g., resist material) inconjunction with the thermal CVD process or by utilizing a moreselective thermal CVD process, such as an energy-beam assisted CVD toselectively heat specific portions of the substrate upon whichdeposition or “writing” of Ru will be performed.

[0032] Many of the processes used for CVD of Ru utilize low pressuresystems. However, no criticality with respect to the pressure in thesystem exists in practicing the present invention. While typicaloperating pressures range from about 0.1 to about 10 torr, higher orlower pressures are also acceptable. These variations in pressure arelargely determined by a number of factors, such as resultant filmconformity, the vapor pressure of the Ru precursor compound, theevacuation speed and efficiency of the vacuum equipment, and physicalcharacteristics of inert carrier gases that can be added to adjust thetotal pressure.

[0033] The growth of a pure ruthenium film can be conducted by utilizingany of the aforementioned CVD methods and apparatus designs, using asolvated ruthenium precursor formulation under conditions whereinreactive gases are absent. Alternatively, RuO₂ films can be formed bycontacting any of the vaporized Ru precursor formulations with a heatedsubstrate in the presence of an oxidizing agent. The oxidizing agent maybe any gaseous reactant which is capable of reacting with the solvatedRu precursor compounds at the decomposition temperatures of the latterto form Ru oxide deposits. Suitable oxidizing agents for use with thepresent method include, but are not limited to, air, oxygen, andoxygen-containing compounds, such as nitrous oxide, ozone, hydrogenperoxide, tetrahydrofuran, water, carbon dioxide, sulfur dioxide, sulfurtrioxide (sulfuric anhydride), organic peroxides, and are preferablyselected from mildly oxidizing gaseous oxygen sources.

[0034] Oxidizing agents may alternatively be introduced into the reactorin combination with a carrier gas. The present method producesconductive RuO₂ films on substrates, such as silicon, when thedepositions are carried out in atmospheres containing the aforementionedoxidizing agents. X-ray photoelectron spectroscopy (XPS) reveals thedeposition of a pure RuO₂ film from (C₆H₈)Ru(CO)₃, the RuO₂ filmexhibiting a constant oxygen concentration throughout the depth of thedeposited film.

[0035] The instant process can be modified by depositing the Ru metalfirst, forming the oxide in situ by oxidizing the Ru metal through anyof the oxidizing processes described herein, and siliciding the bottomlayer of Ru metal. Alternatively, the Ru layer can be oxidized by postdeposition anneal.

[0036] Various other modifications to the process of the instantinvention are envisioned. For example, other metals, alloys, andmixtures thereof can also be incorporated into the solvated precursorformulations and deposited, together with Ru or RuO₂, onto a substrate.Where non-oxidized Ru metal-containing films are desirable, thedeposition is carried out under nonoxidizing conditions. Alternatively,the deposition can be carried out using relatively low flows ofoxidizers or weak oxidizing agents, such as N₂O.

[0037] The processes described herein result in high-quality Ru filmswhich can be deposited at various thicknesses. The thickness of thedeposited layer can be modified by controlling a number of variables,such as the vaporization rate for the Ru precursor formulation, the timeand temperature of deposition, the flow rate of the vapor of the Ruprecursor, the length of contact time between the substrate and the Ruprecursor compounds, and the volatility of the specific Ru precursor andsolvent selected. Products and structures manufactured according to theprocess of this invention can be made to have any desired Ru-containinglayer thickness. A preferred range of thickness for semiconductor orelectronic applications is from a monomolecular layer to about 0.1micron.

[0038] The processes described herein are useful to deposit Ru andruthenium-containing materials (e.g., RuO₂, RuIr, SrRuO₃, RuSi_(x), Rualloys, etc.) onto a substrate, such as a semiconductor substrate, tocreate diffusion barriers, electrode materials, semiconductor dopants,contact metallizations, interconnection traces, and the like. Any of theprocesses described herein advantageously provide low-temperaturedeposition of Ru and RuO₂-containing layers having conformal coverageand excellent step coverage.

[0039] The present invention will be understood more fully from thedescription which follows, and from the accompanying examples, in whichparticular embodiments of the process of the invention are described. Itis to be understood at the outset, however, that persons of ordinaryskill in the appropriate arts may modify the invention herein describedwhile still achieving the favorable results of this invention.Accordingly, the description and examples which follow are to beunderstood as being a broad teaching disclosure directed to persons ofordinary skill in the appropriate arts, and are not to be understood aslimiting upon the present invention. The scope of the invention is to bedetermined by the appended claims.

EXAMPLE I

[0040] Preparation of solvatedtricarbonyl[(1,2,3,4-,q)-1,3-cyclohexadiene]ruthenium

[0041] Tricarbonyl[(1,2,3,4-η)-1,3-cyclohexadiene] ruthenium(hereinafter “(C₆H₈)Ru(CO)₃”) was prepared by mixing 10 gm of Ru₃(CO)1 ₂(Strem Chemicals, Inc., Newburyport, Mass.), 30 mls of benzene (AldrichChemical Co., Milwaukee, Wisc.), and 13.5 ml of 1,3-cyclohexadiene (9equivalents, 0.141 mol) (Aldrich Chemical Co., Milwaukee, Wisc.) in aglass flask. The resulting solution was heated to 80° C. and refluxedfor 48 hours, at which point the solution turned yellow in color.

[0042] Refluxing was halted, the flask was isolated and attached to avacuum line, and the bulk of the benzene was then removed from theflask. The remaining portion of the solution was cannula transferred toa mini-distillation apparatus, where a pressure in manifold of about 6Torr was established. Remaining amounts of benzene and1,3-cyclohexadiene were removed by warming the contents of the flask byheating a mantle to about 30° C. The flask was then heated to about 60°C. under static vacuum and the receiver was cooled in order to removethe product of the reaction, a slightly yellow-colored oil of(C₆H₈)Ru(CO)₃. 2.65 gms. of (C₆H₈)Ru(CO)₃ (0.01 mole) were added to a0.10 liter volumetric flask at room temperature (approximately 20-25° C.(68-77° F.)) and hexanes (a mixture of hexane isotopes) were added toobtain a total volume of 0.10 liters of 0.1M solution of (C₆H₈)Ru(CO)₃in hexanes.

EXAMPLE II Ruthenium Film Deposition from (C₆H₈)Ru(CO)₃ Solution

[0043] The precursor (C₆H₈)Ru(CO)₃ solution, prepared according to thedescription of Example I, was delivered into a flash vaporizer at aconcentration of 0.1M and at a rate of 0.24 ml/min using a syringe pump.A wafer of p-type silicon was placed in the CVD chamber and heated t190° C. (as measured by a thermocouple in direct contact with thesurface of the wafer). Concurrently with the heating of the wafer, thechamber pressure was stabilized at 5.0 Torr with 50 sccm of He used todeliver the (C₆H₈)Ru(CO)₃ vapor to the chamber. The chamber wasevacuated, and the wafer was cooled to room temperature.

[0044] A smooth, highly reflective coating of metallic Ru was formed onthe wafer. X-ray photoelectron spectroscopy (XPS) was used to profilethe film deposited on the wafer. XPS revealed a pure Ru film having athickness of approximately 1700 Å.

EXAMPLE III Ruthenium Oxide Film Deposition from (C₆H₈)Ru(CO)₃

[0045] Deposition of RuO₂ is carried out using a similar method to thatdescribed in Example II, except that O₂ at 50 sccm is added to the Heused to deliver the (C₆H₈)Ru(CO)₃ vapor to the chamber. A one-minutedeposition is then carried out and the wafer is allowed to cool to roomtemperature. A smooth, highly reflective coating of metallic RuO₂ isformed on the wafer.

What is claimed is:
 1. A method of forming a ruthenium film on asemiconductor substrate, the method comprising: providing a rutheniumprecursor formulation comprising tricarbonyl ruthenium dissolved in asolvent; vaporizing said ruthenium precursor formulation to form avaporized precursor compound; and directing said vaporized precursorcompound toward said semiconductor substrate or to form a ruthenium filmon a surface of the semiconductor substrate.
 2. The method of claim 1,further comprising providing said tricarbonyl ruthenium as a liquid. 3.The method of claim 1, further comprising providing said tricarbonylruthenium to have a freezing point around room temperature.
 4. Themethod of claim 1, wherein said tricarbonyl ruthenium decomposes at atemperature greater than room temperature.
 5. The method of claim 1,further comprising selecting the semiconductor substrate from the groupconsisting of a semiconductor wafer, a semiconductor on an insulatorsubstrate, a semiconductor on a sapphire substrate, a semiconductor on ametal substrate, a semiconductor on a nitride, and a semiconductor on aconducting layer.
 6. The method of claim 1, further comprisingvaporizing the ruthenium precursor formulation using a hot wall typechemical deposition technique.
 7. The method of claim 1, furthercomprising vaporizing the ruthenium precursor formulation using a coldwall type chemical deposition technique.
 8. The method of claim 1,further comprising containing the semiconductor substrate within areaction chamber having a pressure of about 0.1 torr to about 10 torr.9. The method of claim 1, further comprising containing thesemiconductor substrate within a reaction chamber having a pressure ofabout 1 atmosphere.
 10. The method of claim 1, further comprisingproviding said ruthenium precursor formulation to further contain anoxidizing agent.
 11. The method of claim 1, further comprising providingsaid tricarbonyl ruthenium to further contain oxygen.
 12. The method ofclaim 1, further comprising directing said vaporized tricarbonylruthenium in combination with at least one oxidizing gas toward thesemiconductor substrate to form a ruthenium oxide film on a surface ofthe semiconductor substrate.
 13. The method of claim 12, furthercomprising providing oxygen as said at least one oxidizing gas.
 14. Themethod of claim 12, further comprising selecting said at least oneoxidizing gas from the group of O₂, N₂O, O₃, NO, NO₂, H₂O₂, H₂O, SO₂,SO₃, organic peroxides, and combinations thereof.
 15. The method ofclaim 1, further comprising injecting said ruthenium precursorformulation into a vaporizer to vaporize said ruthenium precursorformulation.
 16. The method of claim 1, further comprising injectingsaid ruthenium precursor formulation into a flash vaporizer to vaporizesaid ruthenium precursor formulation.
 17. The method of claim 1, furthercomprising selecting said solvent from the group consisting of hexane,hexanes, pentane, heptane, and butylacetate.
 18. A method of forming aruthenium film on a semiconductor structure, the method comprising:providing a ruthenium precursor formulation comprisingcyclohexadienetricarbonyl ruthenium dissolved in a solvent; vaporizingsaid ruthenium precursor formulation to form a vaporized precursorcompound; and directing said vaporized precursor compound toward saidsemiconductor structure to form a ruthenium film on a surface of thesemiconductor structure.
 19. The method of claim 18, further comprisinginjecting said ruthenium precursor formulation into a flash vaporizer tovaporize said ruthenium precursor formulation.
 20. The method of claim18, further comprising selecting said solvent from the group consistingof hexane, hexanes, pentane, heptane, and butylacetate.
 21. The methodof claim 18, further comprising selecting the semiconductor structurefrom the group consisting of a semiconductor wafer, a semiconductor onan insulator substrate, a semiconductor on a sapphire substrate, asemiconductor on a metal substrate, a semiconductor on a nitride, and asemiconductor on a conducting layer.
 22. The method of claim 18, furthercomprising selecting said ruthenium precursor formulation to contain anoxidizing agent.
 23. The method of claim 18, further comprisingproviding said ruthenium precursor formulation to further containoxygen.
 24. The method of claim 18, further comprising directing saidvaporized precursor compound in combination with at least one oxidizinggas toward the semiconductor substrate to form a ruthenium oxide film ona surface of the semiconductor structure.
 25. The method of claim 24,further comprising providing oxygen as said at least one oxidizing gas.26. The method of claim 24, further comprising selecting said at leastone oxidizing gas from the group of O₂, N₂O, O₃, NO, NO₂, H₂O₂, H₂O,SO₂, SO₃, organic peroxides, and combinations thereof.
 27. The method ofclaim 18, further comprising injecting said ruthenium precursorformulation into a vaporizer to vaporize said ruthenium precursorformulation.
 28. The method of claim 18, wherein vaporizing saidruthenium precursor formulation comprises injecting said rutheniumprecursor formulation into a flash vaporizer.